During a biopsy a doctor removes a small sample of your kidney tissue to examine under a microscope, according to the Mayo Clinic.

The Mayo Clinic states that biopsies are typically conducted by inserting a thin needle into the patient’s skin to obtain the tissue sample. According to the Mayo Clinic, doctors usually use an imaging device to help guide the needle.

Once the tissue sample is obtained, doctors will carefully examine it under a microscope to look for signs of damage or disease.

An Iranian military observation aircraft flew within 50 yards of an armed U.S. Navy helicopter over the Persian Gulf this month, sparking concern that top Iranian commanders might not be in full control of local forces, CNN has learned.